Embodiments described in this disclosure relate generally to the field of signal pulse measurement, and more particularly to semi-active laser (SAL) pulse measurement apparatus and methods.
Pulsed lasers are used in a variety of applications, including but not limited to, e.g., LIDAR, laser guidance, remote sensing and identification, active countermeasures, among others. In SAL seeker guidance systems such as shown in simplified FIG. 1, an operator 30 (e.g., onboard an aircraft or on the ground) of a laser designator 20 may “paint” a target 40 with a laser beam 40), and when a missile 50 including a SAL seeker is close enough for some of the laser energy 60 reflected from the target 40 to reach the field of view of a missile 10, a seeker system of the missile 10 detects the laser energy 60, associate the energy with the laser painting, find the direction from which the laser energy is being reflected, and uses the directional information to guide the missile 10 toward the target 40.
Efforts exist to improve performance and cost efficiency of SAL receivers have included focus on detector array sensitivity, in addition to power and size requirements (e.g., development of read out integrated circuits (ROICs.) It is advantageous for pulsed laser receivers to be able to accurately measure the shape of pulses with widths in the 5-20 nanoseconds range, arriving at tens of milliseconds intervals, that may have complex (non-Gaussian) temporal shapes. Conventional SAL receivers typically include a detector array, analog circuitry operably coupled to each of the detector array elements that detects photocurrents induced by photons striking the detector array and supplies corresponding signals to a dedicated temporal processor. New laser technologies enable generation of eye-safe laser energy and detection with InGaAs or HgCdTe detectors that have high capacitance, constraining their size, and requiring larger arrays (or scanning) to obtain a wide field of view (FOV). The temporal processor then compares intensity ratios across the detector array elements to determine the centroid of any detected laser spot, which is provided to the main navigational computer as line-of-sight guidance data. There is a continual demand to reduce the complexity, part count, weight, envelope, and cost of these various components (e.g., optical components, sensors, digital and analog processing elements, etc.).
Thus, what is needed is a more sensitive SAL pulse sensing technology with very high temporal resolution, to sample asynchronous, low frequency pulsed signals with large dynamic range. The inventors have recognized the advantages and benefits associated with improved and new techniques for SAL pulse measurement, and related architectures, that address the size, weight and power related shortcomings of currently available measurement apparatus and methods recognized by those of skill in the art.